Numerous forms of apparatus for producing solid carbon dioxide from compressed and cooled carbon dioxide gas and/or liquid carbon dioxide are known. Such apparatus typically comprises substantial units intended to produce relatively large amounts of solid carbon dioxide, sometimes in tightly packed blocks of dry ice.
U.S. Pat. No. 1,949,179 to Pierce, teaches the provision of liquid carbon dioxide through two tubes depending downwardly inside a foraminous bag through which expanding carbon dioxide gas percolates into a surrounding chamber. The liquid carbon dioxide enters the chamber and is passed through a helical coil surrounding the foraminous bag to be cooled by the expanding carbon dioxide gas leaving the foraminous bag. The carbon dioxide is expanded upon entry close to the bottom of the bag and is collected into a cylinder and piston arrangement by which a user may compact the dry ice snow into a solid block. U.S. Pat. No. 1,981,676, to Stapp is another example of a device of this general type.
U.S. Patent No. 2,307,013, to Batzle, on the other hand, teaches a compact apparatus and a method for producing relatively small bodies of carbon dioxide ice formed into predetermined shapes. A sealed capsule of liquid carbon dioxide is punctured in a way that causes the contents to expand into a chamber against a sliding, spring-biased piston having a cavity formed therein. The expanding liquid carbon dioxide is partially formed into snow to fill the cavity in the piston and to exert a force against the spring to obtain compaction of the resulting dry ice, while a portion of the expanded liquid carbon dioxide escapes past the piston as a gas.
Liquid carbon dioxide is usually stored at about room temperature in a conventional cylinder having an outlet valve and a pressure gauge. Since ideal thermodynamic processes are not realizable, a significant portion of the liquid carbon dioxide turns into cold carbon dioxide gas in the known types of apparatus. This gaseous carbon dioxide is either retrieved and recompressed or allowed to escape to atmosphere. Thus, only a relatively small fraction of the original liquid carbon dioxide is converted into dry ice. It is known to flow the incoming liquid carbon dioxide to its point of expansion through tubes which are cooled by the escaping cold carbon dioxide gas as the process proceeds, e.g., is taught by Pierce, mentioned earlier. Hitherto, however, such counter-flow of the incoming liquid carbon dioxide at room temperature and the escaping cold carbon dioxide gas escaping to atmosphere is usually obtained by simple helical coils which are relatively inefficient, expensive, large and heavy.
A need, therefore, exists for an inexpensive, light-weight, highly portable device that may be readily connected to a source of liquid carbon dioxide at room temperature and, within at most a matter of one or two minutes, efficiently convert small amounts of the liquid carbon dioxide into solid carbon dioxide. Such an apparatus should greatly facilitate inexpensive formation and use of solid carbon dioxide wherever liquid carbon dioxide is available.